Petroleum fuels and crude oils contain normal paraffin hydrocarbon waxes which tend to precipitate and crystallize at low temperatures, causing oil to lose its fluidity. Over a range of temperatures, these paraffin wax crystals continue to aggregate and can solidify the oil. This creates difficulties in transporting the petroleum fuel or crude oil through flow lines, valves, and pumps. Paraffin wax crystals are particularly problematic at lower temperatures and in colder climates where, as the temperature drops and approaches the crude oil's pour point, the transportation of crude oil becomes more difficult. Pour point is defined by the ASTM method D-97 as "the lowest temperature at which the crude oil will still flow when it is held in a pour point tube at ninety degrees to the upright for five seconds." Paraffin wax crystals that have come out of solution also tend to plug flow lines, production tubing, flow lines, screens and filters.
This problem is well recognized, and various additives known as pour point depressants and wax crystal modifiers have been used to change the nature of the crystals that precipitate from the petroleum fuel or crude oil, thereby reducing the tendency of the wax crystals to set into a gel. Generally, wax crystal modifiers possess long segments of repeating saturated carbon chain groups (C.sub.20 H.sub.41 --C.sub.50 H.sub.101) that are contained in or attached to a polymer backbone. These compositions, which are slightly soluble in highly aromatic solvents such as toluene, xylene and heavy aromatic naphtha at moderate temperature (i.e., 68.degree. F.), are added to the petroleum fuel or crude oil to be treated. Typically, these crystal modifiers slowly co-crystallize with the paraffin waxes already present in the petroleum fuel or crude oil and effect morphological changes that retard further crystal growth. However, many of the standard crystal modifiers that are known in the art solidify at temperatures ranging from 30.degree. F. to 140.degree. F. Thus many of the crystal modifiers that are presently available are not particularly useful in the field at cold temperatures or under winter conditions.